Decision on Yucca Mountain

Scientific questions linger as government faces last political hurdle to burying nuclear wastes in Nevada

H. JOSEF HEBERTAssociated Press Writer

Published Sunday, July 07, 2002

AMARGOSA VALLEY, Nev. -- In this desert where government scientists want to entomb the country's nuclear waste, nothing is harder to find than water. Yet the answer to whether tons of radioactive waste can be kept here safely for thousands of years centers on just that -- water.

The irony does not escape Michael Voegele as he scans the arid landscape from atop Yucca Mountain, a ridge of volcanic rock under which the Bush administration wants to bury 77,000 tons of waste accumulating at nuclear power reactors in 31 states.

"All we're studying here is ways water can get through this mountain. That's the whole issue. Everything is about water," says Voegele, who has worked on the Yucca project for two decades and now is its chief scientist.

On average 3 inches to 6 inches of rain falls here annually, but this year the mountain has not seen a drop. Voegele pours some water on a rock. In minutes it evaporates in the desert heat and wind that whips across the mountaintop.

But 1,400 feet below, the seemingly dry volcanic tuff created 12 million years ago contains enough moisture -- and some say enough cracks through which water could travel -- to raise uncertainty over whether the waste will safely be contained thousands of years from now.

Questions over the movement of water through the rocks, or whether seeping water might cause waste canisters to corrode, are unresolved -- even as the $58 billion Yucca project approaches a critical political test in Washington.

In February, President Bush said 20 years and nearly $7 billion worth of study was enough to convince him that the project was scientifically sound. Pending a license from the Nuclear Regulatory Commission, the repository would be open for business by 2010.

But Nevada, which sees itself as the nation's nuclear dumping ground, objected. A final decision on whether the Yucca project will go forward or be scrapped rests with Congress. The House already has sided with Bush; the Senate plans a vote this week.

A work train rumbles for nearly two miles through a 25-foot wide U-shaped tunnel deep into Yucca Mountain. It stops where one day thousands of cylindrical metal waste containers, each 5 feet in diameter and 15 feet long, would be kept.

Some of the isotopes will not lose their radioactivity for a million years. The government must give reasonable assurance the waste will not pose an environmental or health threat for only 10,000 years.

Hundreds of boreholes and markings dot the tunnel wall, many with tags where thousands of rock samples have been taken, reflecting years of scientists' scrutiny of the mountain.

Several tags belong to June Fabryka-Martin, a scientist at the Los Alamos National Laboratory. In 1996, she reported a discovery that altered the scientific debate over Yucca Mountain's suitability as a nuclear waste repository.

In minute amounts of water along several rock faults, including one about 900 feet below the surface and close to the area where the waste would be kept, Fabryka-Martin found traces of radioactive Chlorine-36, a byproduct of nuclear bomb testing. It showed, she said, water had to have migrated from the surface within the past 50 years, evidence moisture was moving much faster than expected.

Project scientists "are about evenly divided" over whether the Chlorine-36 came from nuclear testing or naturally from the rock, says Voegele. In either case, he said, "we are assuming the presence of fast pathways" for water through the mountain.

To compensate, engineers altered the proposed repository design with greater reliance on manmade barriers to contain the waste, instead of depending simply on the geology of the mountain as originally envisioned.

Waste canisters will be made of an exceedingly corrosive-resistant material called Alloy-22 and include titanium drip shields to deflect any moisture.

While once the plan was to seal up the repository after 50 years, officials now are looking at keeping open for 300 years, primarily to observe what happens to the canisters.

That has triggered another scientific dispute -- how "hot" should the repository be?

As used reactor fuel decays, it gives off intense heat, as much as 360 degrees Fahrenheit. Some scientists believe heat is not a problem and will drive moisture out of the rock. Others argue if the surrounding rocks get too hot, the storage casks could be damaged.

Higher temperatures "increase uncertainties and decrease confidence in the performance of waste package materials," Jared Cohon, chairman of the Nuclear Waste Technical Review Board and president of Carnegie Mellon University, testified recently at a Senate hearing.

The board, created by Congress, repeatedly has urged the Energy Department to choose a design that would keep temperatures in the repository below boiling -- 212 degrees Fahrenheit.

The board's argument is that moisture in rocks near the containers will evaporate at high temperatures. When the wastes cool after thousands of years, the moisture will condense onto the containers and contribute to their corrosion.

So far the department has resisted the board's advice.

Energy Undersecretary Robert Card recently told the group that a cooler design remains an option. The hotter design, however, is preferred and will be pursued, he said.

Deep beneath the mountain, Voegele makes clear his preference for keeping the waste "screaming hot" and says a lengthy test program has proven that heat will drive moisture away from the wastes.

Critics of Yucca Mountain are worried about other uncertainties, including volcanic eruptions.

Seven dead volcanoes are within 27 miles but the last eruption was 80,000 years ago. Yucca project scientists calculate that the chance of one occurring within the waste repository over the next 10,000 years is 1 in 70 million.

Relatively mild earthquakes have occurred in the area in recent years, including a tremor last month 15 miles from the mountain. Voegele said it barely registered on monitoring equipment within the tunnel. A decade ago, however, an earthquake of 5.6 magnitude 10 miles away damaged a building at the repository site.

Project scientists in their computer models have assumed a hypothetical 6.5 magnitude earthquake hitting nearby and concluded the repository design "would withstand that kind of force," said Voegele.

All of this amounts to far too many unanswered questions, argues Bob Loux, who heads Nevada's office dealing with Yucca Mountain. The state has filed six lawsuits challenging the project and has pledged to fight every step of the way.

"We're told the science somehow is going to have to catch up to this (political) decision," says Loux.

Energy Department officials contend the science is solid and that there will always be uncertainties when trying to design a facility whose success will be determined thousands of years into the future.

They are confident they can meet an Environmental Protection Agency requirement that radioactive exposure to any individual near the site be no more than 15 millirems a year -- about the same as a single chest X-ray.

Margaret Chu, a former Sandia National Laboratory scientist who now heads the Energy Department's office for nuclear waste, insists that the mountain's geology remains the best barrier, even in face of the new scientific questions.

Card, the energy undersecretary, maintains that the technical issues can be resolved, although changes in the program should be expected even decades after waste shipments begin arriving.